Branched vs. unbranched Pathtracing in SF

After reading some articles about Cycles branched path tracing and seeing some videos about it, I tried to see how BPT works in Superfly. I kind of avoided it previously. I've read claimes that BPT is better done with CPU, while the simpler PT is more for GPUs. In my experiments I did not find a proof for this. Both variants work equaliy well with GPU and CPU, at least on my system.

First thing to notice is that the number of samples are not the same on BPT and PT, so I don't compare the same number of samples. I do compare render times. In BPT, this are my settings:

Here is GND2, rendered in Superfly with Clamshell lights. Both renders took 190 Seconds, you can see the render time and the sample in the file name of the original images, in the Irfanview window title. On the right is the BPT image with 20 samples, I think it's less noisy than the 30 samples PT image on the left.

@bantha I've read a lot of articles on reducing the amount of time it takes to render an image in Cycles. The problem is these suggestions don't translate well between Cycles and Superfly. Unfortunately also, my laptop doesn't have GPU.

In this image, Diffuse samples was set to 2. According to what I've read, this helps with grainy parts of the image which are indirectly lit. The time is not exactly the same, with 274 seconds for the PT render (35 samples) and 299 seconds for the BPT render.

You can clearly see in the image that BPD handles fresnel calculations differently. the reflections are less grainy in the PT image, the bathtub is less grainy in the BPT image.

Things do look better with BPT enabled but it's highly unstable using CUDA unfortunately. Sometimes I can get lucky and a render with a single figure will finish but most times something will crash, either my display drivers or poser.

Click on that "i" in the render options when you select BPT and your video card, it warns you that BPT should be disabled while using GPU rendering.

You need a lot of memory for BPT, and most GPU's will run out of memory in a hurry with even simple scenes depending on how many times it branches out. Even with a 32 gig GPU, you could easily run out.